The invention relates in general to reducing the force required to insert an elastomeric seal in a cavity of a metallic member and in particular to reducing the force required to insert a fuel injector in a fuel rail cup.
A known method for making fuel rail cups is by stamping a strip of metal. The cups only (no tumbling media) are then typically tumbled in a tumbling machine to deburr the cups and remove any cleaning solution. The cups are then attached to a fuel rail by, for example, brazing. The fuel rail with cups attached is dipped in a corrosion protection solution such as zinc-iron. The corrosion protection solution attaches to the fuel rail and cups by an electrochemical plating process. The fuel injectors are then inserted in the fuel rail cups either manually or by a machine.
Problems may arise when inserting the injectors in the fuel rail cups. The injector includes a top O-ring, which provides a seal inside the cup. If the injectors are inserted manually, great effort may be required to force the O-ring inside the cup. If the injectors are inserted automatically by a machine, it is possible that the O-ring may be damaged during the insertion process thereby degrading the seal in the cup and resulting in fuel leakage. Further, if the force required to insert the injector is too great, it is possible that the machine will simply stop the insertion operation for that injector and cup.
The present invention provides a method of reducing the force required to insert an elastomeric seal in a cavity of a metallic member comprising tumbling the metallic member in a tumbling machine with media to decrease surface roughness of the metallic member.
Preferably, the tumbling step includes decreasing surface roughness of the metallic member at least a portion of the member defining an entrance to the cavity. In one embodiment, a number of metallic members is about three times greater than a number of media. The media comprise generally cylindrical pieces having ends angled at about 45 degrees.
The present invention also provides a method of reducing the force required to insert fuel injectors in fuel rail cups comprising tumbling the fuel rail cups in a tumbling machine with media to decrease surface roughness of the cups. Preferably, the tumbling step includes decreasing surface roughness of the cups at least portions of the cups defining entrances to the cups. The method may also comprise inserting a fuel injector having a top O-ring into a fuel rail cup.
In one embodiment, the tumbling step includes tumbling a number of cups that is about three times greater than a number of media. Preferably, the media comprise generally cylindrical pieces having ends angled at about 45 degrees. More preferably, the media are about 0.25 inches long and about 3 millimeters in diameter.
In a preferred embodiment, the surface roughness is decreased from about 0.85 Ra micrometers to about 0.20 Ra micrometers.
The present invention also provides an apparatus comprising a fuel rail cup, the fuel rail cup including an entrance portion and an interior portion, a surface roughness of the entrance portion being less than a surface roughness of the interior portion. Preferably, the surface roughness of the entrance portion is about 0.20 Ra micrometers and the surface roughness of the interior portion is about 0.85 Ra micrometers.
The apparatus may further comprise a fuel injector having a top O-ring, the fuel injector being inserted in the interior portion of the cup. More preferably, the apparatus further comprises a fuel rail, the cup being attached to the fuel rail.